A good way to consolidate the information you have already learned in this TLP is look at how recycling processes are used in a real application, for example the recycling of automobiles. Cars are usually designed with a specific lifespan – around 10 years. This lifespan is steadily decreasing over time because of the increasing speed of development in automobile manufacture. The recycling of automobiles is a partial success story – since on average today 75% by weight of a car is recycled. Still, the amount recycled will have to increase to meet government targets. In the UK, from 2015, a target of recycling 95% by weight of a car was set. Only 10% of this weight can be fuel.
However, 75% by weight does not mean 75% by volume. A large amount of the volume of a car is in the form of plastics and other non-metallic elements such as glass. The recycled volume is almost entirely ferrous metal – virtually none of the non-metallic elements in cars are recycled. This is an issue that will have to be addressed if the new targets are to be met.
There are four stages in the recycling of your average car:
- All fluids are drained from the car, including antifreeze coolant, oil, brake fluid, transmission fluid and washer fluid. In theory, distillation could be used to separate out these liquids and separate especially the oil and grease, which can be used again as fuel or lubricant.
- Easily removable parts of the vehicle are taken out and sorted according to reyclability, whether they can be re-sold (such as the bumpers), or whether they are to be landfilled. The glass windows can be recycled, along with the tyres and a few of the polymeric components.
- Crushing of the remainder of the car.
- Shredding into small particles. These particles can then be sorted by the eddy current separation method explained above, to recover the ferrous and non-ferrous metals from the residual ‘shredder fluff'.
Shredder fluff is currently landfilled, because of the economic costs of separating it out once it has been shredded into fist size pieces. Although landfilling consumes very small amounts of energy, in the UK there are new restrictions on the amount of material that is landfilled. Reasons for this are along the lines of chemicals leaching into the water supply.
Methods are continually being developed to process this residual material so that the new ELV directive can be met (95% of cars recycled from 2015) involving large amounts of research and development in the recycling of polymeric materials, again illustrating the important role materials science plays in improving the sustainability of our planet. Materials developed from biological materials that are sustainable and can be recycled are coming into use, for example, in Ford’s Model-U car.
The Model U is helping encourage development of materials that are safe to produce, use and recycle over and over again in a cradle-to-cradle cycle. These materials never become waste, but instead are nutrients that either feed healthy soil or the manufacturing processes without moving down the value chain.